@article{ARM_1987__23_2_a1,
     author = {Zelinka, Bohdan},
     title = {Neighbourhood digraphs},
     journal = {Archivum mathematicum},
     pages = {69--70},
     publisher = {mathdoc},
     volume = {23},
     number = {2},
     year = {1987},
     mrnumber = {930322},
     zbl = {0626.05018},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ARM_1987__23_2_a1/}
}